How to use a Regulated DC Power Suppy (symmetric) with Rpi 4B

Diy and Tweaks Diy and Tweaks
1

Hi folks, I have a Regulated DC Power Suppy that I want to use for a volumio / RPi 4b streamer project. Its a symmetric Power supply, so the outputs are VSS-, common ground, and VCC+

I’m not an electronics engineer so I’m not 100% on the nature of symmetric power supply. My question is, where to connect to get 5.1v DC for the Rpi? I assume VCC+ and Ground but im not sure as I dont know the reason for VSS-
I really dont want to blow up my Pi
I know that I can adjust the trim pots on each side of the symmetric supply to get my 5.1v, I will do that with a multimeter - I just dont want to short anything or blow it up before I’ve even started.
Many thanks
Steve!
(upload://cx2F4hYc8lL9hDNJtBSx75oVerz.jpeg)

regulated-dc-power-suppy-module-lm317-lm337
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2

you need the middle ground and right vcc+.
you can then set the voltage via a multimeter via the blue pot to 5 volt.
of course keep in mind that you use the correct wires +/- connection to the rapberry pi.

but what I wonder then does this power supply have enough amps to drive a raspberry pi.
do you have a link to the product?

3

Hi,

You do not need a symmetric power supply for the RasPI - you can use VCC+ and Ground, but VSS- will be unused and useless.

Better you replace it by an power supply that delivers more Amperes on only VCC+

Br
Josef

1 Like
4

Thanks guys, it’s a power supply I already had, not specifically chosen for Pi.
It’s 25w with variable output from 2.5 to 18 volts using LM317 and LM337

So 25w at 5 volts is 5 amp, no?

5

depends on how it’s specified.
the LM317 has a max current of 1.5A if I am correct.

image
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6

if I’m right this would be the amperage of the transformer output.

Schermafbeelding 2023-05-28 om 08.57.13
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7

this is the calculation for the input, not for the output

8

you are right, the 25W max output power are calculated with an output voltage of 18V. With An output voltage of 5V, the maximum output power will be lower, because of the 1.5A limit of the LM317

9

And since there are no transistors in the screenshot of the module to boost the current, it will not deliver the needed current.to power the rPi.

10

looks a bit like it.

11

you are right.

12

yup, it originally came from audiophonics, so I think thats it. No good for my pi project then!! Any recommendations that wont break the bank?

13

Think its this one…

14

I have this myself and it won’t work for a raspberry pi.

15

Yup, I guess the 1.5a rules that out. Kind of a waste using a symmetric for this anyway. I’ll keep it for a later date and maybe get a toroidal and a regulated dc board from audiophonics or similar

16

I have a diy linear power supply that is rated at 5V (variable 0-9V) and 5A output. Will a direct connection to the RPi 4 5V GPIO pins harm the RPi?

17

when nothing goes wrong, prob. not. But with a DIY psu, I am pretty sure there is no protection, so if things goes sour, your rPi will be toasted.

Strongly advise against it.

18

I would also advise against this. Yes it is possible, but there is no fuse or anything so it imay be dead if it goes wrong. Especially since your PSU is variable. Also I do not thinks it is a good idea to do 5A max current while the RPI is rated to be at 3A. Technically this does not matter, but as there is no fuse protection, the damage done will be a lot higher. With 3A it may survive (hypothetically), with 5A it may not.

19

Hi, I have been using two of these for my RPI project, and they seem to work quite well. If you order them, they might take a while, and you need to let them know what your input voltage is. I have one powering my RPI and the other powering a 1920x480 monitor.

https://www.aliexpress.com/item/1005003752763281.html?spm=a2g0o.order_list.order_list_main.11.21ef1802u9M9VV&gatewayAdapt=glo2jpn